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Question DetailsAsked on 11/26/2013

Can someone recommend a contractor for removing wetness from a basement wall constructed with concrete slabs?

I have had visits from couple of contractors, who are interested to install inside french drain with additional sum pump and other costly solutions. These folks don't explain their reasons. I am looking for an engineer cum construction type.

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2 Answers

0
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Typically water leaking into a basement comes through the CMU/concrete walls or the floor slab. This is due to water in the surrounding soil. The water builds up and permeates the concrete/CMU. You mentioned a french drain and sump pump - those are the typical solutions for something like this, along with waterproofing installed on the outside of the basement wall. The french drain provides an escape for any water building up outside the wall, so that it doesn't stay there and end up leaking through the wall. (A french drain is typically a perforated pipe surrounded by gravel wrapped in a cloth to prevent washing the soil away. The pipe either "daylights" somewhere that allows drainage, or a sump pump is used to pump the water out, or both.)


So without knowing more about your situation, I'd say that the solutions proposed are sound.


Ryan Briggs, PE

Arx Engineering

Source: http://www.arxengineering.com

Answered 6 years ago by arxengineering

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There are four (common) basic ways of handling water intrusion into a basement - the "best" and cheapest varies depending on how much water you are talking about, water elevation outside the basement, soil permeability, construction materials used in the house, etc:

1) divert water outside the house so it never reaches the foundation, with surface drainage and roof runoff changes. For more info on sources of water problems and how to intercept them check out the prior responses in Home > Basement Waterproofing in the Browse Project section at lower left - there are several pretty exhaustive lists of the common sources of water problems in basements. In probably about 3/4 or more of the ones I have been involved with, diversion of runoff alone or combined with only a sump pump in a corner of the basement solved the problem totally, without any cutoffs, impermeable membranes, or french drains. The beauty of that solution is even if it does not totally work, it will reduce the water flow that any eventual french drain/sump pump system has to handle.

2) intercept water at the foundation face and divert it away with an outside french drain to ground surface away from the house, or to a drywell system or wet well with sump pump, depending on topography and local water table and soil type

3) trench and waterproof the outside of the foundation so water cannot seep through it (usually bitumastic or membrane), or grout the zone outside the foundation to reduce permeability (rarely done for residences).

4) intercept seepage inside the house with french drain or drain channel (typically just under or just on top of the slab at the foundation wall) or trenches in the slab or concrete "dike" at the slab edge (crude way) leading to a sump pump - sounds like this is what they are suggesting to you. Commonly simplest of options 2-4 because does ot involve trenching arond the outside of the foundation, just cutting slots around the perimeter of the slab or installing interceptor channels around the perimeter.

If you are not comfortable with what they are telling you (or have not told you so far, it sounds like), two suggestions:

1) with the ones who looked at it and you feel comfortable with, call and ask WHY they are suggesting that particular method over other alternatives, though that is commonly cheaper than all but intercepting the water before it gets to the foundation in the first place.

2) if you want an unbiased expert opinion (for $250-400 typcially) then a local geotechnical engineer or civil engineer experienced in foundation drainage problems can assess the issue and give you recommendations, as well as probably recommend a contractor or three that he has worked with and trusts. The engineer can provide plans and specifications and on-site construction inspection at added cost, if you want. You will have to search through local civil or foundations engineers, then call to find ones with experience and interest in local residential foundation seepage issues, and then ask them about their rates.

One emphatic recommnedation - do NOT let them talk you into any system that involves drilling holes though your foundation footer or walls to collect water from outside the foundation and running it to a sump pump - drilling holes in your walls to let MORE water in is just plain irresponsible and shows the contractor has no idea what he is doing, and runs the very significant risk of intercepting more water than it can handle in the rainy or snowmelt season, which can lead to flooding of your basement. Intercepting water under the floor slab or on the inside face of the footer is a different thing - there the water is already inside the foundation and is what is causing your problem, so a french drain or suction system picking that water up or channeling it to a sump pump is a common and viable solution. And of course, any sump pump system has to discharge far enough away from the house that the water flow away from the house, and does not just recycle into the basement. I can't count how many houses I have seen with oveloaded sump pumps, where the simplest immediate solution was to just add 10-20 feet of drain pipe or plastic lined ditch to keep the sump pump discharge water from running right back down along the basement walls.

Answered 6 years ago by LCD




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